Preform for multilayer container comprising a polyethylene furanoate layer

ABSTRACT

A preform for multilayer container having a polyethylene furanoate layer includes an outer layer defining an exterior surface and including poly(ethylene terephthalate) and an inner barrier layer including semi-crystalline poly(ethylene furanoate) where the semi-crystalline poly(ethylene furanoate) of the inner barrier layer has a crystallinity in the range of 3 to 10%.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Divisional application of U.S. application Ser.No. 16/807,711, filed Mar. 3, 2020, which claims the benefit ofNetherlands Application No. 2022678, filed Mar. 5, 2019, the contents ofall of which are incorporated by reference herein.

FIELD OF THE INVENTION

The invention relates to a container comprising a layer of poly(ethyleneterephthalate) (PET) and a layer of poly(ethylene furanoate) (PEF), apreform for such a container and a method for producing such acontainer.

BACKGROUND OF THE INVENTION

Poly(ethylene terephthalate) (PET) is one of the most widely appliedmaterials in plastic containers or bottles, due to its excellent barrierand mechanical properties. However, the barrier and mechanicalproperties are still limited for some applications, such as carbonatedsoft drink bottles with a volume lower than 1 L and for packaging oxygensensitive products.

A widely applied solution to this problem is the use of a secondmaterial as an intermediate layer in the bottle wall. Many methods forinjection molding exist that incorporate a middle layer in a preform,which ends up as a thin layer in the wall of the bottle after the bottlehas been blown from such a preform. The most common material used as anadditional layer today is a polyamide, such as nylon-6, nylon-6,6 ornylon MXD 6, that is derived from adipic acid andm-diaminomethylbenzene. Other, less common materials are polyethylenenaphthalate (PEN) and polytrimethylene naphthalate (PTN). Typically thematerial of the additional layer comprises 5-20% wt of the totalmultilayer package dependent on the barrier improvement needed in thefinal package.

Typical known barrier materials are expensive; MXD6 and PEN are threeand five times more expensive than PET, respectively. PTN is even higherin price. The known barrier materials also pose a threat for the PETrecycling stream, because of too different processing temperaturesand/or discoloration and/or haze in bottle walls in the recycledmaterials. Air elutriation and flake sorting steps are needed inrecycling, creating more waste for the recyclers. Problems in recyclingrequire limited use of tie-layers between the barrier layer and the PETlayers. Therefore multilayer PET bottles tend to have poor adhesionbetween the layers, resulting in a squeaking sound and layer separationwhen handling the bottle. In some cases the amount of the barrier layerwhich may be used is further limited, below what a bottle designer maywish for obtaining improved barrier properties, due to incompatibilitywith the recycle process used to reclaim the PET main body. Furthermore,MXD6 does not yield any improvement for water vapour barrier.

In WO 2016/130748 a multilayer container with a barrier layer of PEF, orother furandicarboxylate polyesters or copolyesters, is described.Furandicarboxylate polyester can be used as a barrier material inmultilayer bottles due to its good barrier properties, and such barrierproperties extend across a number of the furandicarboxylate polyestersor copolyesters. According to WO 2016/130748 the furandicarboxylatepolyester is a good barrier material as the CO₂ barrier properties ofPEF are about 7 times better than that of semicrystalline PET and the O₂barrier properties of PEF are about 5.2 times better than those ofsemicrystalline PET. WO 2015/031907 teaches that conventional methodsfor processing PET cannot be successfully applied to PEF in theproduction of containers, such as food and beverage containers. WO2015/031907 therefore provides novel preforms and methods for processingpolymers comprising FDCA to produce such preforms and containers bystretch blow molding.

In this context WO 2016/130748 discloses a multilayer container,comprising an outer layer defining an exterior surface and an innerlayer defining an interior surface and interior space, wherein the outerlayer comprises a PET polyester, and the inner layer comprises a2,5-furandicarboxylate polyester, e.g., PEF. Although reference is madeto semi-crystalline PET it appears that amorphous PEF is used in thecontainers shown in WO 2016/130748.

SUMMARY OF THE INVENTION

It is an object of the invention to further improve PET-containerscomprising barrier materials, and especially those containingfurandicarboxylate polyester. It is a further object of the invention toimprove PET-containers comprising PEF. This is achieved according to afirst aspect of the invention by a container comprising an outer layerdefining an exterior surface and comprising poly(ethylene terephthalate)and an inner barrier layer comprising semi-crystalline poly(ethylenefuranoate). Poly(ethylene furanoate) is also known aspoly(ethylene-2,5-furandicarboxylate).

DETAILED DESCRIPTION OF THE INVENTION

The invention is based on the recognition that the use ofsemi-crystalline poly(ethylene furanoate) instead of amorphouspoly(ethylene furanoate) not only further improves the barrierproperties of poly(ethylene furanoate) but also allows for thinnerbarrier layers, which leads to a reduced PEF-content and thus easierrecycling and also a reduced effect on the color of the resultingrecyclate. With a reduced barrier thickness also multilayer containerscan be produced as colourless and haze-free containers. Additionally theinvention includes the recognition that with a semicrystalline barrierlayer comprising poly(ethylene furanoate) the shelf life of thecontainer is improved. Furthermore PEF has the advantage that it hasbarrier properties which are relatively independent of moisture, incontrast to for example nylon MXD6, allowing a more consistentperformance independent of environment. The advantages of the inventionfurther include the recognition that use of semi-crystalline barrierlayer of PEF avoids the negative impact on PET recyclability whichcertain other barrier materials exhibit, because PEF can be processed atsimilar conditions as PET and has the ability to form a miscible system,resulting in haze-free materials in the recycle stream. The recyclesystem is further improved, as the crystallinity of the PEF layer makessubsequent additional crystallization, drying, and any solid-statepolymerization (if desired) to be less burdensome.

The barrier improvement factor (BIF) of amorphous PEF andsemi-crystalline PEF versus semi-crystalline PET is shown in Table 1.These factors can be found in bottles and films. The BIF is defined asthe permeability of a gas through the film or piece of bottle wall,divided by the permeability of the gas through a film or bottle wall ofsemi-crystalline PET at the same temperature and pressure.

TABLE 1 Barrier Improvement Factor (BIF): comparison of BIF of amorphousand semi-crystalline PEF vs. BIF of semi-crystalline PET Amorphous PEFSemi-crystalline PEF O₂ 2-6 8-10 CO₂ 4-7 8-11 H₂O 1.2 2-3 

As WO 2016/130748 describes a BIF for PEF of 7.9 for CO₂ and a BIF of5.2 for O₂ it is evident that WO 2016/130748 relates to amorphous PEF.

In the following, embodiments of the invention are described. Theembodiments described herein can be combined if not explicitly describedas alternatives.

In a preferred embodiment the poly(ethylene furanoate) has acrystallinity X_(c) of at least 5%. In an even more preferred embodimentthe poly(ethylene furanoate) has a crystallinity X_(c) of 15 to 40%. Thehigher the crystallinity is the greater is the improvement in thebarrier improvement factor over PET and the shelf life. Thecrystallinity is preferably measured via differential scanningcalorimetry (DSC) and given as %, where the % crystallinity iscalculated on the first upheat of the sample, and the net meltingenthalpy is divided by the enthalpy of 140 J/g, which represents a 100%PEF crystallinity, and then multiplied by 100:

$\begin{matrix}{{Crystallinity}\mspace{14mu}{X_{c} = \frac{\Delta H_{{melt}\mspace{11mu}{({net})}}}{\Delta H_{melt}^{O}}}} & \left( {{Equation}\mspace{14mu} I} \right)\end{matrix}$

with ΔH_(melt (net)) being the net melting enthalpy measured at thefirst upheat of the sample and ΔH^(O) _(melt) the equilibrium meltingenthalpy taken at 140 J g⁻¹ for PEF.

Preferably, the following method is employed. The barrier layer iscarefully removed from the bottle side-wall panel where the bottlediameter is the largest, and circles with a 5 mm radius are cuttherefrom and placed in the bottom of a DSC pan, after which they areheated at 10 K min⁻¹ from 25 to 265° C.

Advantageously a layer thickness of the inner barrier layer is in arange of 0.001 mm to 0.5 mm, preferably in a range of 0.005 mm to 0.1mm. As previously described thinner layers of PEF in PET containerscould be easier recycled and the color brightness of the PET containercan be maintained. A typical bottle has 0.2-0.3 mm wall thickness,thinner bottles may have a wall thickness of 0.1 mm. Thus a barrierlayer thickness of 0.001 mm, or 1% of the wall in a thinner bottle isrealized. In thicker bottles of 0.5 mm wall thickness with 20% PEFbarrier layer the PEF layer can be up to 0.1 mm. For thermoformingcontainers a range of 0.005-0.5 mm is preferred, corresponding to a wallthickness of 0.1-1 mm with 5-50% PEF barrier layer.

In a further embodiment the poly(ethylene furanoate) has a content ofdiethylene glycol below 2 wt %, based on the poly(ethylene furanoate).Such a low content of diethylene glycol is favorable as it enhances thecrystallization process. The formation of diethylene glycol is forexample suppressed by adding a DEG suppressant, modifying theesterification process or using a continuous polymerization process. Asuitable method for the preparation of PEF with a low DEG contentcomprises a process, wherein a starting mixture comprising2,5-furandicarboxylic acid and ethylene glycol or comprising a dialkylester of 2,5-furandicarboxylic acid and ethylene glycol is subjected toesterification or transesterifiaction to form an ester composition,which ester composition thus obtained is subjected to polycondensationat reduced pressure in the presence of a polycondensation catalyst toobtain a polycondensate, wherein the esterification ortransesterification takes place in the presence of a basic compoundand/or an ammonium compound capable of suppressing the formation ofdiethylene glycol. Suitable compounds include tetraalkyl ammoniumcompounds, choline, alkali metal salts of carboxylic acids, alkalineearth metal salts of carboxylic acids, basic alkali metal salts ofmineral acids, basic alkaline earth metal salts of mineral acids, alkalimetal hydroxides, ammonium hydroxides and combinations thereof. Asuitable method has been described in WO 2015/137805.

Although it is preferred that no diacid moieties, other than2,5-furandicrboxylate and optionally some other aromatic diacids, arepresent in the composition, it is acceptable for small amounts of acidsor anhydrides with functionality of three or more, used as branchingagents, for example at a level of 0.15 mol % or less. Such agents canactually improve the level of crystallinity when used to create abranched architecture and a resultant increase in strain hardening.

The addition of diols during the polymerization process, other thanethylene glycol, is generally disadvantageous, due to a reduction on theextent of crystallization of the PEF resin layer. Thus, preferably, theonly added diol is ethylene glycol.

Although it is preferred that no diol moieties other than the ethyleneglycol moiety are in the composition, it is possible to add low levels,for example less than 0.15 mol %, of moieties with three or more hydroxyunits, such as pentaerthyritol or others, which may be added asbranching agents. Such agents can actually improve the level ofcrystallinity when used to create a branched architecture and aresultant increase in strain hardening.

Having a PEF layer with an intrinsic viscosity (IV) which is higher thanthe viscosity of the PET layers lead to further enhancement ofcrystallization during the bottle blowing process. In one embodiment theIV of the PEF portion of the preform is preferably at least 0.03 dL/ghigher, and more preferably at least 0.05 dL/g higher, and mostpreferably 0.07 dL/g higher than the PET layer(s). Advantageously, theIV of the PEF portion is at most 3.5 dL/g, more preferably at most 0.25dL/g, higher than the IV of the PET portion. The intrinsic viscosity isconveniently measured for PET using 60/40 w/w phenol/tetrachloroethaneat 25° C., following ASTM D4603. The IV of the PEF layer is measuredusing the same method. The IV is determined on the preform. As analternative, e.g., if the preform is not available the IVs of the bottlecan also be used, as relatively little drop in IV is experienced duringthe bottle blowing process.

As an example of this principle, if the PET portion of the preform hasan IV of 0.79 dL/g, then the IV of the PEF layer is preferably at least0.82 dL/g, more preferably at least 0.84 dL/g, and most preferably atleast 0.86 dL/g.

The container comprises in some embodiments an additional inner layerdefining an interior surface and comprising poly(ethyleneterephthalate), wherein the inner barrier layer is arranged between theouter layer and the inner layer. Alternatively the inner barrier layeritself defines the interior surface.

In some embodiments the container is a bottle.

According to a second aspect the invention relates to a preformcomprising an outer layer defining an exterior surface and comprisingpoly(ethylene terephthalate) and an inner barrier layer comprisingsemi-crystalline poly(ethylene furanoate). Such preform is also known asa pre-nucleated preform. The poly(ethylene furanoate) in the preformsuitably has a crystallinity X_(c) of at least 2%, preferably in therange of 3 to 10%.

The semi-crystalline or pre-nucleated poly(ethylene furanoate) in thepreform can be achieved, e.g., by preparing the polymer with anucleating agent. This infers the presence of crystalline nuclei in thepoly(ethylene furanoate). This allows for some crystallinity of thepolymer in the preparation of the preform from a melt. The preformproduction process may also be modified by manipulating cooling timesand increasing mold temperature, such as the temperature of the mold incontact with the poly(ethylene furanoate), in order to induce morecrystallinity in the preform. These steps may be done in a process whichis separate from the normal injection molding or blow molding processes.

Another method is obtained by flow-induced crystallization. Flow ofmolten polymer is known to induce crystallization, which is referred toas flow-induced crystallization. Such is explained in, e.g., US2009/163666.

In a further embodiment the preform comprises an additional inner layerdefining an interior surface and comprising poly(ethyleneterephthalate), wherein the inner barrier layer is arranged between theouter layer and the additional inner layer, and is achieved bysimultaneous co-injection of both materials.

It is preferred that the preform comprises poly(ethylene furanoate) witha content of diethylene glycol of at most 2 wt %, based on thepoly(ethylene furanoate).

According to a third aspect the invention relates to a method of makinga container comprising

providing a preform according to the second aspect of the invention, andstretch blow-molding the preform to a container.

The preform according to the second aspect of the invention and themethod according to the third aspect share the advantages described inthe context of the container according to the first aspect.

It shall be understood that the container of the first aspect of theinvention and the preform according to the second aspect of theinvention have similar or identical embodiments.

It is preferred that the stretch blow-molding comprises a relaxationstep. Such a relaxation step enhances the crystallization of PEF andthus leads to improved containers as described in the context of thefirst aspect of the invention.

The relaxation step is in some embodiments performed with a moldtemperature of at least 15° C., preferably at least 30° C. and/or a holdtime of at least 1 s, preferably at least 2 s in the mold. Both thetemperature and the holding time may vary widely. The upper temperatureis suitably 90° C., preferably 75° C. The holding time may be up to 15min, preferably up to 10 min. It is further advantageous, if therelaxation step is performed in a mold of a material with a thermalconductivity below 5 W/(m*K), preferably of a non-metal material. Thisallows for a low cooling rate during the relaxation step and thusfurther enhances the crystallization. In some embodiments providing thepreform comprises a polymerization process of a resin, wherein 10 to10,000 ppm (mole/mole) of at least one of terephthalic acid, isophthalicacid or other aromatic diacids and/or at least one crystal nucleatingagent is added. These measures enhance the crystallization of PEF duringthe production process.

The addition of acids during the polymerization process, other than2,5-furandicarboxylic acid, also is generally disadvantageous due to areduced extent of crystallization. The addition of certain aromaticdiacids is acceptable at levels of 10 to 10,000 ppm (mol/mol). Thesearomatic acids are preferably selected from the group comprisingterephthalic acid, isophthalic acid, naphthalene dicarboxylic acid, orcombinations thereof. These acids have surprisingly been found have theability to increase the crystallinity of PEF resins. Preferably, noother diacid moieties are added to the composition.

Nucleating agents may be added to the poly(alkylene furandicarboxylate)to increase the nucleation density, and thereby increase the overallcrystallization rate under quiescent conditions. The nucleating agentsmay act as seeding particles to promote crystallization. The nucleatingagents may suitably be selected from the group consisting of inorganiccompounds, organic salts, organic acids, high melting waxes, polymersand combinations thereof. The high melting waxes suitably have a meltingpoint in the range of 50 to 150° C. High melting waxes include materialssuch as stearamides and erucamides, or bis-amides.

When the nucleating agent comprises a polymer such polymer suitably iscrystalline or semi-crystalline. Suitable polymers include the groupconsisting of PET, PBT, PEG, poly(ethylene-co-methacrylic acid),poly(ethylene-co-acrylic acid) and combinations thereof.Poly(ethylene-co-methacrylic acid) and poly(ethylene-co-acrylic acid)are so-called ionomers. Some ionomers are commercially available, e g.Surlyn ionomers from Du Pont, or Aculyn ionomers from Dow or Aclynionomers from Honeywell.

When the nucleating agent comprises an inorganic compound the inorganiccompound is preferably selected from the group consisting of talc,titanium dioxide, silica, boron nitride, metal carbonate, clays, metalsilicates and combinations thereof. The metal carbonate may comprise analkali metal or an alkaline earth metal. Hence, the carbonate can besodium or potassium carbonate, or calcium carbonate. It is also possibleto use salts with other metals, such as zinc carbonate. The metalsilicates may be selected from alkali metal silicates, such as sodiumsilicate, and alkaline earth metal silicate, such as calcium ormagnesium silicate. Very suitably the silicates used are clays orzeolites, such as sepiolite (magnesium silicate clay), mordenite(aluminumsilicate containing alkali metal, alkaline earth metal and/orhydrogen ions). Other natural silicates may also be employed, such asmica. Silica may also be used. When silica is used in the nucleatingagent, the silica may be natural crystalline silica such as sand orquartz or amorphous fused silica. The silica or silicates may beselected from naturally occurring minerals (e.g. sepiolite, mica,quartz), but also from synthetic silica or silicates (e.g. fused silica,synthetic zeolites).

When the nucleating agent comprises an organic compound, the compoundmay be an organic acid. In such a case, the nucleating agent preferablycomprises an organic acid, selected from the group consisting ofaromatic carboxylic acids, heteroaromatic carboxylic acids, saturatedheterocyclic carboxylic acids, unsaturated heterocyclic carboxylicacids, hydroxyl group-containing mono- and diacids having from 4 to 12carbon atoms, and combinations thereof.

Examples of an aromatic acid include benzoic acid, furoic acid,2,5-furandicarboxylic acid, pyrimidine carboxylic acid (also known asorotic acid), pyridine carboxylic acid, tetrahydroxy hexanedioic acid(also known as mucic acid). Preferably, the nucleating agent comprisesan organic salt. Such an organic salt suitably comprises a metal anionand an organic cation. The metal anion is suitably an alkali metal ionor an alkaline earth metal ion. Examples are the sodium, potassium,calcium and magnesium ions. The cation may be derived from a wide rangeof organic compounds, which typically include an acid functionality. Theacid functionality may be provided by any of the acids that arementioned above as suitable organic acid included as such in thenucleating agent. The nucleating agent preferably comprises an organicsalt of the group selected from a metal salt of an aliphaticC₈-C₃₀-carboxylic acid, an optionally substituted aromatic acid, anoptionally substituted aromatic diacid, an optionally substitutedcycloaliphatic dicarboxylic acid and combinations thereof.

When these acids are substituted, the substituent may suitably be aC₁-C₆ alkyl group, a C₁-C₆ alkoxy group, a hydroxyl group, a halogenatom, a nitro group, sulfonyl-containing moieties or any combinationthereof. Suitable aliphatic acids include stearic acid, oleic acid,lauric acid and montanic acid. Suitable aromatic acids include benzoicacid, phthalic acid, isophthalic acid, terephthalic acid, naphthalenecarboxylic acid, naphthalene acetic acid and any combination thereof.Examples of suitable heterocyclic acids include furoic acid,furandicarboxylic acid.

In addition, other nucleating agents may be included in the nucleatingagent in the masterbatch composition according to the present invention.Such additional nucleating agents are e.g. aromatic phosphonates,sulfonic acid ester salts of isophthalic acid, bis(4-10propylbenzylidene) propyl sorbitol and 3.4- dimethylbenzylidene sorbitolphosphate salts and esters, available as NA-11,methylene-bis(4,6-di-t-butylphenyl)phosphate sodium salt, or NA-21,aluminium-hydroxy-bis[2,2″-methylene-bis(4,6-di-t-butyl-phenyl)-phosphate.

The most preferred organic compounds are saccharin (i.e.2H-1λ⁶,2-benzothiazol-1,1,3-trione), and the metal salts of saccharin.The nucleating agent therefore preferably includes saccharin or a saltof saccharin, wherein the salt may be selected from alkali and alkalineearth metal salt. Suitable examples are the sodium salt of saccharin andthe calcium salt of saccharin. It has been found that the use of themetal salts of saccharin provides excellent crystallization results.

Preferably providing a preform comprises providing a resin ofpoly(ethylene furanoate) and of poly(ethylene terephthalate) andinjection molding the resins to provide a preform. Two separate partscan be injection molded that form a single preform, or PET can beinjection molded in a mold cavity containing a molded PEF article, in aprocess called overmolding. Alternatively, PEF and PET can beco-injected into a preform in a single step.

EXAMPLES

In table 2 and 3 examples of 250 ml bottles and the improvement in shelflife due to semi-crystalline PEF as barrier layer instead of a pure PETbottle or a PET bottle with Nylon MXD6 barrier layer are shown.

The shelf life test is carried out as a calculation similar to the onedescribed for PET bottles in M. Profaizer, Italian Food and BeverageTechnology, 48 (2007) 1-6.

The crystallinity X_(c) was determined using a Mettler-Toledo DSC 1equipped with the STAR software, calibrated using In and Zn standard.For this, the barrier layer was carefully removed from the bottleside-wall panel where the bottle diameter is the largest, and circleswith a 5 mm radius were cut therefrom and placed in the bottom of a DSCpan, after which they were heated at 10 K min⁻¹ from 25 to 265° C.

The crystallinity X_(c) is calculated from the integrated DSC peaks viathe following equation:

$\begin{matrix}{{Crystallinity}\mspace{14mu}{X_{c} = \frac{\Delta H_{{melt}\mspace{11mu}{({net})}}}{\Delta H_{melt}^{O}}}} & \left( {{Equation}\mspace{14mu} I} \right)\end{matrix}$

with ΔH_(melt (net)) being the net melting enthalpy measured at thefirst upheat of the sample and ΔH^(O) _(melt) the equilibrium meltingenthalpy taken at 140 Jg⁻¹ for PEF.

TABLE 2 Shelf life Example 1 2 3 4 5 Volume (mL) 250 250 250 250 250Weight (g) 21.0 21.0 21.0 21.0 21.0 Main PET PET PET PET PET materialBarrier — Nylon PEF Nylon PEF material MXD6 MXD6 Barrier layer — 5 10 510 (% w/w) Blow mold 15 15 15 70 70 temperature (° C.) Barrier layer —26 7 29 24 crystallinity (%) Shelf life 10 25 18 27 26 to −17.5% loss,starting from 4.2 Vol. (wks)

TABLE 3 Shelf life Example 6 7 8 9 10 11 Volume (mL) 250 250 250 250 250250 Weight (g) 25.0 15.0 15.0 15.0 15.0 15.0 Main PET PET PET PET PETPET material Barrier — Nylon PEF Nylon PEF — material MXD6 MXD6 Barrierlayer — 5 10 5 10 — (% w/w) Blow mold 15 15 15 70 70 15 temperature (°C.) Barrier layer — 28 9 30 28 — crystallinity (%) Shelf life 12 12 9 1313 7 to −17.5% loss, starting from 4.2 Vol. (wks)

As can be seen from tables 2 and 3 the shelf life of an all-PET bottleincreases with at least 7% for every weight percent of PEF added as abarrier layer. Furthermore, the shelf life of an all-PET bottle isincreased with between 9% and 10% for every weight percent of PEF addedas a barrier layer, when the bottle is subjected to a relaxation step,like using a hot mold or non-metal mold material. On the other side,while maintaining the same shelf life, the total weight of an all-PETbottle can be reduce by more than 2% for every weight percent of PEFadded as a barrier layer. And while maintaining the same shelf life, thetotal weight of an all-PET bottle can be reduced by between 3% and 5%for every weight percent of PEF added, when the bottle is subjected to arelaxation step.

The invention claimed is:
 1. A preform comprising an outer layerdefining an exterior surface and comprising poly(ethylene terephthalate)and an inner barrier layer comprising semi-crystalline poly(ethylenefuranoate) wherein semi-crystalline poly(ethylene furanoate) of theinner barrier layer has a crystallinity in the range of 3 to 10%.
 2. Thepreform according to claim 1, comprising an additional inner layerdefining an interior surface and comprising poly(ethyleneterephthalate), wherein the inner barrier layer is arranged between theouter layer and the additional inner layer.
 3. The preform according toclaim 1, wherein the poly(ethylene furanoate) has a content ofdiethylene glycol of at most 2 wt %, based on the poly(ethylenefuranoate).
 4. A method of making a container comprising: providing apreform according to claim 1, and stretch blow-molding the preform to acontainer.
 5. The method according to claim 4, wherein the stretchblow-molding comprises a relaxation step.
 6. The method according toclaim 5, wherein the relaxation step is performed with a moldtemperature of at least 15° C., preferably at least 30° C. and/or a holdtime of at least 1 s, preferably at least 2 s, in the mold.
 7. Themethod according to claim 5, wherein the relaxation step is performed ina mold of a material with a thermal conductivity below 5 W/(m*K),preferably of a non-metal material.
 8. The method according to claim 4,wherein providing the preform comprises a polymerization process ofresin, wherein 10 to 10,000 ppm (mole/mole) of at least one ofterephthalic acid, isophthalic acid, naphthalene dicarboxylic acid, orother aromatic diacids and/or at least one crystal nucleating agent isadded.